Music Trade Review

Music Trade Review -- © mbsi.org, arcade-museum.com -- digitized with support from namm.org
FEHKIJAKV 2, 1924
THE MUSIC TRADE
REVIEW
11
The Wherefores of Lumber Drying
First of a Series of Articles by Thomas D. Perry, Vice-President and Manager of the Grand Rapids Veneer
Works, Grand Rapids, Mich., on the Principles of Lumber Drying, Operating Tests, Different
Types of Kilns in Use and Their Accessory Equipment
AN anyone imagine a piano, or an organ,
made entirely without wood, or a piano
case, an action, a keyboard, or a sounding
board made chiefly of metal? Experiments
have been made, it is true, on metal backs, metal
sounding boards and metal actions; but they
have never achieved either an artistic or a com-
mercial success. What would be the resulting
musical quality of a violin, a guitar or a 'cello
without the resonance of the products of the
tree? In bulk, more than 80 per cent of a
modern player-piano is made from wood, and
more than 50 per cent by value and weight.
What research, or handbooks, or instructional
artisanship, or scientific development has been
devoted to discovering and mastering the under-
lying principles, and practical application of the
same, to the efficient and economic construction
of the wooden parts of a piano, or other musical
instrument?
Lumber Famine
Our country, in fact the world, will be literally
face to face with a demonstrable shortage of
lumber within the next fifty years, and the
lessening reserves of hardwood will be threat-
ening within two decades, "or within the indus-
trial experience of most men now in charge of
our music trades production.
What are we doing about it, or what do we
propose to do to avert this menacing shortage?
Are we intelligently utilizing our present pur-
chases of lumber, with due caution against ex-
cessive waste, and careful consideration for the
maximum degree of strength, permanence and
beauty?
Such searching questions and statements as
these are a challenge to the present-day wood-
worker, and may well cause him to stop, listen
and think.
A prerequisite to the continuation and
growth of the music industries is an adequate
replenishment of our supply of timber reserves,
and every member of the trade should stand
firmly for such conservation. But an equally
important obligation rests on us all, and that is
the intelligent and economical use of the wood
supply we still possess.
Drying Essential
* The first and fundamental operation, after the
conversion of the tree into lumber or boards, is
C
ment in kilns. The usual border line between ting this schedule of temperature and relative
the two forms of moisture is in the vicinity of humidity the accompanying graphic chart is
30 per cent moisture content (the percentage of
the weight of water removed being computed on
STEAMING
DRYING
200 :
3 too
the dry-fiber weight as a base). It is possible
to use artificial means to remove this free moist-
—1
ure, but a simple air exposure is usually more
t
economical.
__
Looking at the end of a board, it is obvious
9*
lhat air drying removes more moisture from the
surface than from the center, and that, because
125 cr
a
of the width and length of a board, drying takes
5
place chiefly through the flat faces rather than
PERIOD Of" .DRYING
through the ends or edges. The inevitable
result is a surface drier than the interior, and
Figure 2
air-dried stock is therefore subject to an internal The drying cycle divides itself into two phases: initial
strain that often>manifests itself in the form of "steaming" or high-humidity period, in which lumber is
through and enough moisture added to make the
warp, twist or other surface irregularity. The heated
surface as wet as the center; and final "drying," when
humidity
may he gradually dropped and temperature raised
problem is to draw the center moisture out and within limits
demanded by the kind and condition of
the lumber.
leave the surface and interior equally dry.
The skill of an engineer is not required to obtained. The temperature should gradually
rAOl
Grains of Water Vapor per Cubic Foot at Various Relative Humidities
COPYRIGHT 11 24 BV T H E GFUMD RAPIDS VF.NEV R WORKS
ALL RIGHTS RESERVED
( 7000 GRAINS = 1 LB • WOIRDUPOIS )
KELATIVE HUMIDITY
DEO
FAHH.
5%
lo 1 ':
l'.'.;.
1
1
3
3
4
5
5
4
5
5
6
7
5
6
7
8
9
3V
40 r
45%,
507,
65%
00%
8
9
10
7
8
9
11
12
8
9
10
12
14
9
10
12
14
15
10
11
13
15
17
11
13
14
17
19
12
14
16
18
20
LiO%
6
TEMPERA-
« %
70%
75%
80%
85%
50%
05%
100%,
13
15
17
20
22
14
16
18
21
24
15
17
20
23
26
16
18
21
24
27
17
19
22
26
29
18
21
24
27
31
19
22
25
29
32
20
23
26
30
34
115
120
DO;
FAHR
100
105
110
115
120
2
2
2
2
3
3
3
125
130
135
140
145
2
2
3
3
3
4
4
5
6
6
6
7
8
8
10
8
9
10
11
13
10
11
13
14
16
12
13
15
17
19
14
15
18
20
22
16
18
20
23
26
18
20
23
25
29
20
22
25
28
32
22
24
28
31
35
23
26
30
34
38
25
29
33
37
42
27
31
35
39
45
29
33
38
42
48
31
35
40
45
51
32
37
43
48
54
35
40
45
51
58
37
42
48
54
61
39
44
50
56
64
125
130
135
140
145
150
155
160
165
170
4
4
4
5
6
7
8
9
10
11
11
12
13
15
17
14
16
18
20
22
18
20
22
25
28
21
24
27
30
34
25
28
31
35
39
29
32
36
40
45
32
36
40
45
50
36
40
45
50
56
39
44
49
55
61
43
48
54
60
67
46
52
58
65
73
50
56
63
71
78
54
60
67
76
84
57
65
72
81
89
61
69
76
86
95
64
73
81
91
101
68
77
85
96
106
72
81
90
101
112
150
155
160
165
170
175
180
185
190
195
200
6
7
8
8
9
10
12
19
21
23
25
28
31
25
28
31
31
34
38
41
37
15
17
44
48
54
59
65
72
50
55
61
68
75
82
56
62
69
76
84
92
62
70
77
84
94
103
69
76
84
93
103
113
75
83
92
101
112
123
81
90
100
110
122
133
87
97
107
118
131
144
94
103
115
127
140
154
100
110
123
135
150
164
106
117
130
144
159
175
113
124
138
152
168
185
119 125
131 138
146 153
160 169
178 187
195 205
175
180
185
190
195
200
]
k4
19
2)
34
3?
41
4>
51
1
41
46
51
56
62
ADAPTED FROM TABLES COMPILED BY DR. WILLIAM M. GROSVENOR, WITH
READINGS INTERPOLATED AND DECIMALS PISCARDEE
100
105
no
INTERMEDIATE
Figure 3
(Full-page copies of table supplied gratis by author.)
discover that, if the drying of wood afforded no
organic difficulties, the equations and formulas
of moisture removal would be simple. As a
matter of fact, the nature of wood is the one
phase of the problem that engineers least appre-
ciate. It is almost axiomatic to say that wood
should not be subject to external or internal
Figure 1
strain during drying, but such a "strainless"
The heavy shading toward the center indicates greater
moisture content. The fresh sawed end of a partially dried
condition is practically impossible to achieve.
hoard will often show similar effect, but without shading
The reduction of this drying strain to a mini-
or coloring.
to properly dry the wood that is destined to mum is necessary to the drying of the lumber
without damage, the usual manifestations of
comprise the major portion of our musical in
struments of the future. Nature has put this which are checking, warping, honeycombing,
moisture in the tree as a means of growth, and hollow-horning, etc. The chance of internal
"the removal of this water is necessary to secure: strain greatly increases with the thickness of
the wood to be dried: e. g., one-sixteenth-inch
1. Reduction of excess weight.
veneer is practically all surface and can develop
2. Development of strength and stiffness.
3. Elimination of shrinkage, warping and little internal strain in any kind of drying, while
four-inch green birch or maple is a decidedly
other internal strains.
4. Permanence of dimension and shape in fab- stubborn drying problem and taxes the skill of
the best operator in an efficiently controllable
rication.
kiln.
5. Preservation of resonant qualities.
Typical Drying Cycle
6. Durable and beautiful surface finishes.
Before considering the individual characteris-
Water Exists in Two Forms
This water content of wood exists in two tics of the various types of kiln, it may be well
to outline briefly a drying cycle. Take an actual
forms, free moisture and cell moisture, the for
mer being readily evaporable in ordinary air operation schedule, tested by practice, of reduc-
drying, and the latter demanding either exces- ing 8/4 maple from 35 per cent moisture content
sive air drying (several years) or artificial treat- to 5 per cent in 16 days of 24-hour steam. Plot-
rise from 125 to 170 degrees Fahrenheit, and
care should be exercised that it does not go up
too fast during the initial steaming, which would
tend to crust the outside of the boards. The
relative humidity line reaches 100 per cent as
rapidly as possible without producing an excess
of temperature. The reason for the high initial
STEAMING
'DPY;NG
r-
-—
a
5
r
I
u.
±1
i_j
1
a
a
/
5OK
\
T ^ * -
t
^ -
150° g
—
a
K
J Zbi
a
o%
cr
1
PERIOD OF DRVN6
Figure 4
Similar to preceding graph, with addition of moisture deficit
expressed in grains per cubic foot. This moisture deficit
may be termed the measure of potential drying power.
humidity is that partially dried lumber, as placed
in the kiln for drying, normally has a surface
drier than the interior; and unless the surface
is thoroughly moistened, the internal moisture
will be sealed in by the dry and shrunken sur-
(Continued on page 12)